SAN DIEGO -- Authorities believe that a car left running overnight in a condominium garage that sent ten people to the hospital with carbon monoxide poisoning may have started accidentally.

Three people in the garage's adjacent unit were seriously impaired when fire fighters arrived on the scene Saturay morning.

"Two were unconscious and one was very disoriented," said a responder with the Chula Vista Fire Department.

Fire fighters were called to the Huntington Point Road complex at 7 after a resident couldn't wake up the other two people in the unit.

"This type of gas is odorless and tasteless. It can't be seen or smelled," said the investigator, who asked that his name not be used. "We were called because one of the people tried to wake up the other people.

"When the (fire) engine got there, they realized the car had been running and the garage door was very hot," he said.

The air quality of the closest unit was 145 parts of carbon monoxide per million -- which is more than seven times the normal atmospheric level of 25 parts per million, authorities said.

Symptoms of carbon monoxide poisoning include headaches, dizziness, nausea, flu-like symptoms, confusion and impaired judgement.

Rescuers found seven more affected people from within the multi-unit building and rushed them all to the hospital, the investigator said.

There is no word yet on whether anyone will be charged.

"It seemed like a total accident. No one knows how it happened," he said. "Maybe with further investigating we'll know more."